ABSTRACT Most current rock physics work on unconventional resources focuses on the present-day rock properties such as velocity and pore pressure. However, present-day properties are controlled by a rock’s burial history. Here we present an inclusion-based, geologically-constrained rock physics model for pore pressure prediction. Based on a (geo)time-space view of rocks, we simulate the evolution of physical properties due to the varied diagenetic processes that control rock composition, pore systems, etc. through time. Once calibrated, the model can be used to predict pressure via integration of well log, SEM, and geohistory data. Data from the Eagle Ford are used to demonstrate the concept. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 1:50 PM Presentation Start Time: 3:30 PM Location: Poster Station 1 Presentation Type: Poster

ABSTRACT Several parameters within the minimum horizontal stress (σh) equation are difficult to solve for without an extensive core database (e.g. Biot coefficients and strain values). There is also some debate as to which form of the stress equation to use (isotropic versus anisotropic, assuming tectonic stress or a ‘zero lateral strain’ model). The purpose of this paper is to review these parameters and equation forms and to test them in a geomechanical model that was created from a reasonably large database of seismic, logs, and engineering data. The results of this investigation indicate that an isotropic solution to the stress equation should never be used in a basin that contains organic mudrocks. Whether the tectonic term is used or not is not critical. There are some advantages to using it but often strain values are not known with any certainty. A solution for Biot coefficients is proposed that shows promise but needs further testing with core data. Finally, calibration of σh with DFIT and completion data demonstrate that the solutions are reasonably accurate but that deep Wolfcamp stresses need to be assessed in more detail (which is not in the scope of this paper). Presentation Date: Tuesday, September 17, 2019 Session Start Time: 1:50 PM Presentation Start Time: 2:40 PM Location: 217A Presentation Type: Oral

ABSTRACT The flowback rate of hydraulic fracturing in shale gas wells is low. During fracturing and blowout, large amount of fracturing fluid enters the pores of shale matrix from the fracture end face under the action of capillary force and chemical osmosis. The reservoir shale is compact, and the clay minerals with micro-nano pore sizes can effectively serve as semi-permeable membranes. There is a chemical potential difference between fracturing fluid and the reservoir pore fluid, and the fracturing fluid is chemically coupled with the shale reservoir matrix. Considering the deformation of fracturing fluid and reservoir rock, under the framework of porous media, hydraulic and chemical interactions affect the fluid system composed of fracturing fluid and formation fluid. In this paper, a model considering mechanical interaction between solid and liquid phases, coupling effect of solute diffusion and the induced pore pressure by chemical osmosis between shale gas reservoir and fracturing fluid was established. Considering the porosity and permeability of reservoir shale, the spatial and temporal variation of induced pore pressure and fluid solute concentration under chemical action is analyzed. According to the differences of shale fractures and matrix structures, the interaction between in-situ fracturing fluid and shale reservoir is analyzed respectively. Presentation Date: Wednesday, September 18, 2019 Session Start Time: 8:30 AM Presentation Start Time: 9:45 AM Location: 305 Presentation Type: Oral

ABSTRACT Machine learning can play an important role in making subsurface quantitative interpretation workflows more efficient, consistent and potentially more accurate. Two workflows are shown in 1D and 3D applications. It is argued that the 1D cases are more about improving efficiency whilst the 3D cases have the potential to improve the accuracy. Examples are shown from conventional and unconventional basins. Beyond that it is demonstrated how one can combine deep learning and physics-based models to provide fast and accurate subsurface predictions. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Start Time: 3:05 PM Location: 217A Presentation Type: Oral

ABSTRACT Numerical modeling of dynamic rupture propagation is a well-established technique in investigations of large tectonic earthquakes. We develop a methodology to integrate that technique with the modeling of fluid flow in deformable porous media to study properties of the fault zones and the stress state in the subsurface. We perform the analysis of May 17, 2012 Mw4.8 Timpson, TX earthquake. We build a simplified geologic model and run the suite of simulations. We find that even in unfavorable orientation of maximum horizontal stress relative to fault strike, the fault can slip if it was critically stressed initially. We also find that more complex stress states and fault zone properties than depth-dependent-only ones are needed to reproduce the Mw 4.8 earthquake. Presentation Date: Wednesday, September 18, 2019 Session Start Time: 1:50 PM Presentation Time: 4:45 PM Location: 302B Presentation Type: Oral

ABSTRACT In recent years, the oil and gas prospectors pay more and more attention of glutenite reservoir, especially the man who worked in the fault basin. Glutenite reservoir is a kind of subtle reservoirs. Due to the prospectors didn't research the relationship between the reservoir characteristic parameters and seismic elastic parameters, we lack of theory support and rock physics test in the glutenite. Especially for continental faces glutenite, predecessors didn’t research the relationship how to changed seismic elastic parameters the sedimentary characteristics, the diagenetic environment and diagenetic process. This project mainly study rock physical characteristics of the continental glutenite reservoir. Firstly, we test the rock physics characters of the samples in the study area. Then under the guidance of the theory of rock physics, we will statistically and analyzed the data of the test. The ultimate aim is to establish a rock physical model which can be applied to the glutenite reservoir. The relation will be used to describe the glutenite reservoir. We chose 10 wells in a china basin and collected 82 samples of permeability glutenite reservoir. Using the results of the rock physical characteristics testing of these samples, a new kind of porepressure prediction model is established, and obtained good application effect. Presentation Date: Tuesday, September 17, 2019 Session Start Time: 8:30 AM Presentation Start Time: 11:00 AM Location: 305 Presentation Type: Oral

ABSTRACT Accurate pore pressure prediction helps to prevent catastrophic incidents including well kicks and blowouts in situ, being of considerable importance in safety and costeffective well design and keeping away geologic disasters. The conventional forecasting methods for pore pressures generally utilize a relation between the vertical effective stress and physical parameters, and the theory of effective stress is usually involved. However, the normal compaction trend is inevitably required in the commonly used Eaton’s equation, which cannot be estimated accurately. In this study, the normal compaction velocity and bulk modulus of shale are simulated by anisotropic shale rock physics modeling to improve the accuracy of the normal trend. Since the bulk modulus and the seismic wave velocity can be converted to each other, we have tried to propose a method for predicting pore pressures from bulk modulus. Firstly, the relation between pore pressure and bulk modulus is initially derived. Furthermore, the elastic impedance equation in terms of bulk modulus is given as forward solver for inversion. Prestack seismic inversion based on Bayesian theory is utilized and then the normal compaction velocity and bulk modulus are simulated through anisotropic shale rock physics modeling. Finally, the pore pressure predicted by the new method is compared with that by Eaton’s velocity equation and the measured pore pressure in a work area of Sichuan Basin, and the difference are small, which verifies the feasibility of the bulk modulus approach. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Time: 2:40 PM Location: 221B Presentation Type: Oral

ABSTRACT Understanding the pore pressures and stress distribution within the subsurface is of paramount importance in the design of a well in order to accurately determine the allowable drilling window. Many of the conventional methods that exist to predict the pore pressures and stresses within shale sequences assume isotropic properties. This paper presents a pragmatic, data-driven approach in order to deal with anisotropy by utilising all the data types from the interpretation of well, drilling and pore pressure data. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Time: 4:45 PM Location: 217D Presentation Type: Oral

ABSTRACT Due to their low permeability, achieving economic production from unconventional reservoirs entails hydraulic fracturing to increase the surface area in contact with the reservoir. Important to the design of efficient hydraulic fractures is an understanding of pore pressure, the orientation and magnitude of principal stresses, the geomechanical properties of the rock, and the density and orientation of any natural fractures. Such understanding can be achieved by building a predictive 3D mechanical earth model, using amplitude variation with angle inversion of properly processed, imaged, and well-calibrated surface-seismic data. This approach requires quantifying the intrinsic anisotropy of shales, azimuthal anisotropy due to the presence of natural fractures and horizontal stress anisotropy, as well as transforming dynamic elastic properties to static elastic and geomechanical properties. Presentation Date: Monday, September 16, 2019 Session Start Time: 1:50 PM Presentation Start Time: 2:15 PM Location: 301B Presentation Type: Oral

ABSTRACT Pore pressure is a critical input to a geomechanical model and impacts the mechanical stability of a well. It is also desirable to map the high pressure areas before drilling decisions are made as wells that intersect these zones are typically more prolific producers. A well-based workflow was developed that was able to predict the recorded pore pressure and then calibrate a geomechanical model which matched the wellbore measurements. This model was then tested on wells with the requisite log dataset and was able to replicate the observed mechanical wellbore behavior, highlighting the accuracy of the pore pressure prediction. The resultant models were then applied to a high resolution 3D seismic inversion encompassing key elastic properties and facies prediction to produce a 3D understanding of the distribution of pressure and stress. Presentation Date: Monday, October 15, 2018 Start Time: 1:50:00 PM Location: 206A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT To approximate seismic wave propagation in double porosity media, the effective Biot governing equations with complex frequency dispersion characteristics are numerically solved using an upscaled poro-visoelastic approach. We compute the wavefields for solid particle velocity and fluid flux in the frequency domain using a mixed grid finite difference method. A homogeneous full space model with a single Cole-Cole relaxation function representing the attenuation mechanism is used to show that the numerical solutions match well the analytical solutions for source centre frequencies of 10 Hz to 10 Hz. The computed pore pressure wavefield for a two-layer porous model is used to further validate our numerical method. Presentation Date: Monday, October 15, 2018 Start Time: 1:50:00 PM Location: 205A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT We present a novel, geomechanically based approach to basin modeling, the primary objective of which is robust prediction of pore pressure and effective stress. Models incorporate the geologic history of a system, accounting for processes including deposition, compaction and structural deformation in a fully coupled thermal-poro-mechanical framework. We describe important features of the model, we present a workflow for construction and calibration of models to subsurface data and interpretation, we demonstrate an application of the approach to a mini-basin in voluminous salt, and we demonstrate that results differ significantly from those of a conventional basin model. Presentation Date: Wednesday, October 17, 2018 Start Time: 8:30:00 AM Location: 209A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT Pore pressure prediction plays an important role in shale gas exploration and fracking technology. The pore pressure in shale cannot be directly measured but to be inferred by the normal compaction trend, so methods based on the effective stress theory are dedicated to establishing a function between seismic interval velocity and pressure. Among them the mostly used method is Eaton’s equation. However, how to precisely quantify the state of compaction remains unsolved. In this study, the AVO/AVA simultaneous inversion was introduced to estimate P-velocity. According to the exponential relationship between the pore pressure and the ratio of velocities, three different methods including the fitting method, the direct calculation method and the model-based direct calculation method based on the Eaton’s equation were used to estimate shale gas pore pressure, respectively. And then a comparative analysis was performed to see the impact of normal compaction trend on the result. It was found that the horizontal continuity of the model-based direct calculation method was the best. The result shows that the approach of estimating the normal compaction trend impacts the pore pressure significantly. Presentation Date: Monday, October 15, 2018 Start Time: 1:50:00 PM Location: 210A (Anaheim Convention Center) Presentation Type: Oral

Summary Development of High Pressure, High Temperature (HPHT) petroleum reservoirs demands the understanding of temperature effects on reservoir properties as well as models including temperature effects. Using an extension to Biot’s effective stress equation, we derived estimates of the nonisothermal effective stress in the deep North Sea Basin. We found that compared to the conventional isothermal effective stress the non-isothermal effective stress is smaller and results indicate that at great depth a neutral effective stress exists so that the post-Triassic formations are floating on the highly overpressured older layers.

ABSTRACT Multi-stage hydraulic fracturing increases production from extremely low-permeability unconventional reservoirs by simultaneously inducing slip on pre-existing fracture planes. Here we illustrate how the high pore pressure generated during hydraulic fracturing operations induces slip on pre-existing fractures and faults with a wide range of orientations, thus creating an interconnected permeable fracture network. We demonstrate the basic principles of stimulating slip on poorly oriented faults using the stress state for a horizontal well in the Barnett Shale where fracture orientation data are also available from an image log. We compare this analysis with independent fracture orientation data obtained from earthquake focal plane mechanisms. Using the stress data, we are able to determine which nodal plane slipped in each microseismic event. As the two analyses yield essentially identical results, they show the basic processes by which slip on planes of varied orientations occurs during hydraulic stimulation. We extend this analysis to address some misconceptions about the likelihood of slip on horizontal bedding planes and planes parallel and perpendicular to horizontal principal stress directions. Notably, we show that inducing slip on horizontal or sub-horizontal bedding planes is nearly impossible except in compressive (reverse to strike-slip/reverse) stress states (S = S ˜ S) or when ambient pore pressure is extremely high. The latter case results in very small differences in the magnitudes of the three principal stresses, regardless of the regional stress state. Presentation Date: Wednesday, October 17, 2018 Start Time: 8:30:00 AM Location: 202A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT The traditional methods to image the salt bodies do not consider near-salt stress perturbations caused by the salt, and the associated velocity perturbations of elastic seismic waves in the sediments near the salt. To demonstrate the importance of stress changes caused by the salt on accurately imaging salt bodies, we develop and apply a combined method of geomechanical stress modeling and salt imaging in this study. We find that when the effects of near-salt stress perturbations are not considered, the imaging of the salt sphere is clearly distorted, and the depth of the salt sphere boundary in the imaging results deviates from its true depth significantly. Furthermore, the imaging results without including near-salt stress perturbations are very poor in the resolution of the salt sphere. In contrast, when we consider the effects of near-salt stress perturbations, the imaging of this salt sphere accurately matches the true salt sphere both in shape and position. The results in this study show that the near-salt stress perturbations should not be ignored in salt imaging, and provide scientific insights for petroleum geologists and exploration geophysicists on the relation between the stress perturbations induced by the salt and accurate imaging of salt structures. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 205A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT We use a workflow that combines various sources of information, such as mud weights, well logs, basin history, and diagenesis, to model pore pressure-velocity relationship based on rock physics principles. This produces velocity templates, which can be used to build velocity models for imaging and inversion. We apply this workflow to a data set from the Gulf of Mexico. We study the diagenesis of shale, particularly, smectite-illite reaction. From well logs, we build models for velocity-porosity and density-overburden relations. Thermal history is approximated from available Bottom Hole Temperature (BHT) data and depositional history is inferred from interpreted horizons. We use mud weight data to calibrate pore pressure-velocity transformation. A number of different pore pressure gradient scenarios result in different velocity profiles or templates. The integration and calibration of many sources of data in this workflow ensure the resulting velocity model is geologically feasible and physically plausible. Presentation Date: Monday, October 15, 2018 Start Time: 1:50:00 PM Location: 202A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT Pore pressure is closely tied to microseismic triggering mechanisms and fluid transport properties of rocks. Pore pressure evolution in the subsurface is commonly described as a linear diffusion phenomenon. Recently, the theory of nonlinear diffusion has been formulated to account for the dependence of permeability on pressure and used to predict microseismic event fronts. We used finite differences to simulate pore pressure diffusion and studied the effects of nonlinearity on microseismicity. Our numerical examples show that in the nonlinear regime, pore pressure diffuses more slowly, shapes more like a wave front, and induces more microseismic events that propagate a greater distance than in the linear regime. Presentation Date: Tuesday, October 16, 2018 Start Time: 9:20:00 AM Location: Poster Station 19 Presentation Type: Poster

ABSTRACT The effective stress coefficient determines the influence of confining and pore pressures on rock properties. We measured the permeability of the Lockatong mudstone sample as a function of pore and confining pressures. Using our established laboratory protocol for such measurements, we estimate the effective stress coefficient for permeability. We use an initial stress cycle to remove the effects of inelastic deformation and microfractures due to core damage. The permeability values lie between 1.8 µD (in the first stress cycle) and 100 nD. The effective stress coefficient for permeability is found to be greater than one (nk = 1.28) at the lowest differential stress. We observe a strong dependence of effective stress coefficient with differential pressure – effective stress coefficient decreased from 1.28 at 2.5 MPa to 0.65 at 60 MPa. The measured permeabilities obey a simple power law dependence on the calculated effective stress. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 202A (Anaheim Convention Center) Presentation Type: Oral

ABSTRACT Measurements of unjacketed pore space compressibility are attempted through a new experimental device which records directly the amount of fluid expelled or taken by the pore space of 16 sandstones during stress cycles under constant differential stress. The complexity of the work resides in taking into account all the errors impacting the measurements. Results show that could have significant relevance for sandstones whose mineral moduli are closer to the classical Qz values. This research is an initial window into relevance and impact of Brown and Korringa theory in poroelastic composites. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 202A (Anaheim Convention Center) Presentation Type: Oral